I wrote myself a similar tool for myself using NRefactory so I can fill you in: I found that converting 10k of C# was incredibly quick and the overall build ti

I wrote myself a similar tool for myself using NRefactory so I can fill you in: I found that converting 10k of C# was incredibly quick and the overall build time was still totally dominated by the slow TypeScript compiler. You are right that the development time is spent unit-testing C# and very rarely invoking the TS compiler so rather than making the workflow worse, it improves it immeasurably. The alternative to recompile TS each time and use Karma and Chrome dev tools is unbearably slow and clunky in comparison. The real win I was after was that the quality of the test tools and debugger for .Net. Using a tool like TestDriven.Net from visual studio so from a r-click I have test coverage, performance, edit-and-continue and all the benefits of the Visual Studio debugger. The generation to typescript is more of a publish step than part of the development cycle. I also convert the NUnit tests to Jasmine so I run the same test suite across the generated javascript. This does catch issues because there are differences, like lexical scoping, that my cs2ts tool did not try to solve.